In recent years, implantable medical device (IMD) technology has rapidly advanced. Sizes and weights of these devices have decreased, while functionality has increased. These advances have created a corresponding demand for improved two-way communication, or wireless telemetry, between the IMD and an external programming device, such as an IMD programmer. Current wireless telemetry systems are designed to provide two-way telemetry by radio frequency (RF) signal transmission between an antenna coil located within the IMD and an antenna coil located in a programming head of the IMD programmer. The programming head can be positioned over the patient's IMD implant site for wireless programming or interrogation of the implanted device. Command instructions or data that are downloaded to the IMD are referred to as downlink transmissions, and data transmitted from the IMD to the IMD programmer device are referred to as uplink transmissions.
The IMD programmer device typically communicates with the IMD using a designated carrier frequency. This RF carrier signal is modulated with transmitted data using modulation or encoding schemes that include, but are not limited to, pulse position modulation (PPM), frequency shift keying (FSK), differential binary phase shift keying (DBPSK) and burst counting (active and inactive states). A polling circuit in a receiver of the IMD programmer typically polls for a downlink transmission signal on a periodic basis. If an antenna of the IMD resonates above a threshold frequency, for example, the receiver in the IMD programmer will be powered up to enable the IMD to communicate with the IMD programmer in a wireless telemetry session. This process of enabling the receiver of the IMD for a telemetry session is often referred to as a “wake-up”. However, not all signals received by the IMD antenna are true downlink transmissions. Electromagnetic noise, out-of-band RF signals, and other interference may be received by the antenna of the IMD and cause false “wake-ups” of the receiver of IMD, unnecessarily drawing current from the IMD battery. After attempting to process an incoming signal, the IMD may determine that the data is a false signal and power down the receiver, i.e. put the telemetry processing and receiving circuitry in a low power or sleep mode.
Preserving battery life is a primary consideration in the design of new implantable medical devices. Reducing the number of times that the receiver of the IMD “wakes up” from a power saving sleep mode to a full-powered telemetry session mode prevents current drain of the battery. Accordingly, there remains a need for a medical device communication system and associated method for operating a medical device RF receiver for discriminating between true downlink RF signals and noise as well as providing other related power and space savings solutions.